Scientists grow mice kidneys in rats
February 6, 2019
Scientists in Japan have successfully used mice stem cells to grow kidneys in rat embryos, a study published on Tuesday showed.
The process has previously been used to grow pancreases in rats, but it's the first time that scientists have grown kidneys.
The technique could in the future help grow human kidneys in animal embryos and combat a severe shortage of donors for people with renal disease.
But the scientists cautioned that the development was just a first step and that "serious technical barriers and complex ethical issues" remain before the technique could be used to develop human organs.
The researchers first identified rat embryos in which the kidneys could be grown. They then genetically-modified the embryos to ensure they did not develop kidneys of its own.
The embryos were then injected with pluripotent stem cells from mice and implanted into rat wombs so they could be carried to term.
Pluripotent stem cells are a kind of "master" cell that can develop into any of the cells and tissue that make up the body.
Curious case of rats and mice
The mice stem cells produced functional kidneys in the rats, the study showed. But the scientists failed to grow functional kidneys when they injected rat stem cells into similarly modified mice embryos.
"Rat stem cells did not readily differentiate into the two main types of cells needed for kidney formation," said Masumi Hirabayashi, an associate professor at Japan's National Institute for Physiological Sciences, who supervised the study.
Conversely, "mouse stem cells efficiently differentiated... forming the basic structures of a kidney," he told AFP news agency.
It's not clear what caused the difference but the researchers believe "environmental cues" inside the mice are likely to blame and not the technique.
Rats die
The rats in which the kidneys were grown died shortly after birth because they did not suckle properly.
The scientists believe that removing the genes that allow kidneys to develop in the womb likely also removed their sense of smell, so the newborns failed to detect milk and died.
The short lives of the rats meant the researchers could not test the functioning of their kidneys. But Hirabayashi said the organs appeared functional "based on anatomical observations."
Ethical concerns
Developing human organs in animals also poses serious ethical questions because human stem cells could develop into brain or reproductive organ cells in the host.
"The main ethical concerns are the risk of consciousness and/or gamete (reproductive cell) production," said Hirabayashi.
"There are serious technical barriers and complex ethical issues that must be discussed and solved before producing human organs in animals," he added.
In the short-term, researchers are likely to focus on ways to genetically modify host rats without lethal side effects.
ap/aw (AFP)